Electronic article surveillance (EAS) systems are generally known in the art for the prevention or deterrence of unauthorized removal of articles from a controlled area. In a typical EAS system, EAS markers (tags or labels) are designed to interact with an electromagnetic field located at the exits of the controlled area, such as a retail store. These EAS markers are attached to the articles to be protected. If an EAS tag is brought into the electromagnetic field or “interrogation zone,” the presence of the tag is detected and appropriate action is taken, such as generating an alarm. For authorized removal of the article, the EAS tag can be deactivated, removed or passed around the electromagnetic field to prevent detection by the EAS system.
Radio-frequency identification (RFID) systems are also generally known in the art and may be used for a number of applications, such as managing inventory, electronic access control, security systems, and automatic identification of cars on toll roads. An RFID system typically includes an RFID reader and an RFID device. The RFID reader transmits a radio-frequency carrier signal to the RFID device. The RFID device responds to the carrier signal with a data signal encoded with information stored by the RFID device.
The market need for combining EAS and RFID functions in the retail environment is rapidly emerging. Many retail stores that now have EAS for shoplifting protection rely on bar code information for inventory control. RFID offers faster and more detailed inventory control over the bar code. Retail stores already pay a considerable amount for hard tags that are re-useable. Adding RFID technology to EAS hard tags could easily pay for the added cost due to improved productivity in inventory control as well as loss prevention.
Dual technology tags that operate as an EAS tag and an RFID tag are described in U.S. Patent Application Publication No. 2008-0068177, which is incorporated herein by reference in its entirety. This Publication discloses the use of a single resonance RFID antenna that is tuned to a desired operating frequency by adjusting a length of the RFID antenna. Due to the narrow band response of this antenna, it is necessary to tune the antenna to a specific frequency depending on the telecommunications regulations of the country or region in which the tag is deployed. For example, the European Telecommunications Standards Institute (ETSI) and the US Federal Communications Commission (FCC) each specify different frequency ranges for EAS/RFID systems. A tag design tuned to a single RFID resonance frequency cannot be used in both European and the U.S. markets. Producing multiple versions of the tags which are tuned for use in multiple markets adds to production costs.
Therefore, what is needed is an RFID antenna that provides a wide enough bandwidth to allow use in multiple frequency regions.